From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A6906C432BE for ; Tue, 10 Aug 2021 13:54:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 83D0C60EE7 for ; Tue, 10 Aug 2021 13:54:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242066AbhHJNyv (ORCPT ); Tue, 10 Aug 2021 09:54:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:60680 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242049AbhHJNyr (ORCPT ); Tue, 10 Aug 2021 09:54:47 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A9DB560C51; Tue, 10 Aug 2021 13:54:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1628603665; bh=iZVe72SbKuxsmlEfQJAIxK+047leBdbzspxxFb3QTIw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=mwtzNQBsWp3FF0MicMHTwkCaY7xXwDSrbnA+HDswEO28Ba4sBu0YcK9o4KMd8+mW7 fHhjZhU+EQoJW67SntsdiXkwrBvQWozAROBeCn/Y+mPnTmHJGna4wSOU0uWDJcWmdg yqZCXggNVEAb4CX/UEvV8sq/34kIqm6Zfj52ItMc64jpJSIrX/qM0gN9+uLAEDByJU WIkG7DUlSy4+B8SPs2us0TZm+oUybKJoHIei6K4A1Z2CaaUTFmTH1Xfcd/IBK3m8yH fFsoqx9qoPqKyueyn4yFo9teaJqedza1PsnYPhSfEDMCSAlLS+n4pA+MhBOdu1QkqO ROKXmGsinF29g== Date: Tue, 10 Aug 2021 06:54:23 -0700 From: Jakub Kicinski To: Ido Schimmel Cc: Andrew Lunn , netdev@vger.kernel.org, davem@davemloft.net, mkubecek@suse.cz, pali@kernel.org, vadimp@nvidia.com, mlxsw@nvidia.com, Ido Schimmel Subject: Re: [RFC PATCH net-next 2/8] ethtool: Add ability to reset transceiver modules Message-ID: <20210810065423.076e3b0d@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> In-Reply-To: References: <20210809102152.719961-1-idosch@idosch.org> <20210809102152.719961-3-idosch@idosch.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, 10 Aug 2021 16:05:07 +0300 Ido Schimmel wrote: > > Again, i'm wondering, why is user space doing the reset? Can you think > > of any other piece of hardware where Linux relies on user space > > performing a reset before the kernel can properly use it? > > > > How long does a reset take? Table 10-1 says the reset pulse must be > > 10uS and table 10-2 says the reset should not take longer than > > 2000ms. > > Takes about 1.5ms to get an ACK on the reset request and another few > seconds to ensure module is in a valid operational state (will remove > RTNL in next version). Hm. RTNL-lock-less ethtool ops are a little concerning. The devlink locking was much complicated by the unclear locking rules. Can we keep ethtool simple and put this functionality in a different API or make the reset async? > > So maybe reset it on ifup if it is in a bad state? > > We can have multiple ports (split) using the same module and in CMIS > each data path is controlled by a different state machine. Given the > complexity of these modules and possible faults, it is possible to > imagine a situation in which a few ports are fine and the rest are > unable to obtain a carrier. > > Resetting the module on ifup of swp1s0 is not intuitive and it shouldn't > affect other split ports (e.g., swp1s1). With the dedicated reset > command we have the ability to enforce all the required restrictions > from the start instead of changing the behavior of existing commands. Sounds similar to what ethtool --reset was trying to address (upper 16 bits). Could we reuse that? Whether its a SFP or other part of the port being reset may not be entirely important to the user, so perhaps it's not a bad idea to abstract that away and stick to "reset levels"?